Employees walk inside Wison Engineering Services Co Ltd in Shanghai in this September 3, 2013 file photo. Wison Engineering Services Co Ltd, a major PetroChina supplier, said Chinese authorities investigating the company had seized records and temporarily frozen some of its bank accounts, adding it was no longer able to contact its chairman. Shanghai-based Wison had previously said chairman and founder Hua Bangsong had been assisting authorities in an unspecified investigation, which coincides with a probe into oil giant PetroChina and its parent, China National Petroleum Corp (CNPC). REUTERS/Aly Song/Files (CHINA - Tags: BUSINESS COMMODITIES ENERGY) less&nbsp